A double-blind, randomized study compared the effects of placebo, propranolol, nifedipine and the combination of propranolol and nifedipine on exercise capacity in patients with atherosclerotic coronary artery disease. The only drug intervention which produced a prolongation of bicycle exercise time was the combination of propranolol and nifedipine and the improvement was slight. The dose schedule for nifedipine may explain its reduced effect, but it is uncertain propranolol was ineffective.